The invention relates to the use of foams to enhance oil recovery. Foams in the oil industry are basically used in three different applications. The first application is for blocking the breakthrough of water or gas that is being used as a secondary oil recovery technique by pushing the oil to a receiving well. The foam flows to the higher permeable zone in the formation and acts to decrease the permeation of that zone, in order to block the breakthrough. The second application is for using the foam itself as an agent to push the oil to a receiving well in secondary oil recovery. The final application is the use of foams in low density drilling muds to aid in removal of drilling debris.
Typically surfactants, for example, fluorinated surfactants, are used for these applications because they can efficiently and effectively foam both water and oil, without emulsification. Since the fluorinated surfactants do not participate in emulsification, less surfactant can be used, offsetting the cost of fluorinated surfactants. Fluorinated surfactants are also the surfactants of choice in these applications because they remain surface active under the harsh conditions experienced in an oil formation, e.g., high temperature/pressure, high electrolyte concentrations, etc.
The foams produced from using fluorinated surfactants are very stable. However, this stability can be an issue once the foams are recovered on the surface, since it is desirable to break these foams for further work-up of the produced oils. Another undesirable characteristic of surfactant is that they can leave residue behind on the formation.